This invention relates to a pack of the flexible, easy-opening bag type, particularly for a liquid or liquid-containing food product.
Certain liquid or liquid-containing products, for example mozzarella, are sold in sealed flexible bags known as flow packs.
This type of pack has the advantage of being economical: it uses very little packaging material and enables the bags to be continuously filled during production. In addition, it is environment-friendly because the plastic packaging material, for example polyethylene, can be destroyed without emitting pollutants. The bags in question are also practical and compact and can be printed on their outer surface either with a message or with a trade mark.
Packs of the type in question have to be impervious, i.e. they have to withstand the pressure of the liquid and must not allow any losses of product, particularly in the interests of storage. This explains why they do not normally have an easy-opening system because conventional systems comprise pre-cuts or weakened lines in the actual wall of the bag which is not compatible with the need for imperviousness.
Finally, removal of the products from the packs for consumption involves the cutting or piercing of a sufficiently large opening, normally with a pair of scissors, to allow the liquid to flow out and the product to be subsequently removed. The liquid in the bag inevitably spills out during this operation and splashes the user.
In one known pack and process for packaging a product in a bag, the tear strip for easy opening is applied by heat sealing to the longitudinal edges of a tubular film and is used to seal the tube longitudinally. See, for example, U.S. Pat. No. 3,373,926. This system requires the application of a line of antisealing material at the ends of the tear strip to allow the formation of gripping tabs. A pack of this type is intended for the packaging of dry products of the snack type and is not suitable for the envelopment of liquid products where the bag has to be impervious and the sealing zones resistant.
To achieve impervious sealing, the tear strip would have to be wide and applied precisely along the longitudinal edges of the film. The longitudinal sealing zones along the strip would necessarily be narrow. The formation of an anti-sealing zone during the lateral sealing phase would require perfect adjustment and synchronization of the tools used for laterally sealing and cutting the bags and the lateral sealing zone would be narrow at this point. All these factors would multiply the risk of losses in the packaging of a liquid product applying pressure to the sealing zones during the filling and handling of the bags.